Lobot -- Bring Him Back
Let's get this out of the way first: Lobot deserves his own movie. Heck, Lobot deserves his own Syfy channel series. This dude gets no respect in Empire Strikes Back, and he's like the most powerful guy in the movie. He's essentially a human computer (or cyborg) who has his head rigged up so that his brain is literally connected to Cloud City's central computer. Sure, you might think he's quietly playing Angry Birds the whole time while war breaks out, but you just know he's secretly plotting everyone's demise instead.